Hybrid nonlinear block encoded continuous phase frequency shift keying

A block encoding approach is known to be an effective technique to increase the minimum Euclidean distance of continuous phase frequency shift keying (CPFSK) signals. R.H.-H. Yang et al. introduced rate-1/2 hybrid linear block encoded CPFSK to increase the Euclidean distance (see ISPACS, 2003). However, for a higher coding rate, namely rate-2/3, no useful hybrid linear encoder has been found. Two alternative hybrid nonlinear block encoders, viz., nonlinear/nonlinear and nonlinear/linear, are applied to CPFSK, to achieve larger inevitable merging intervals and prevent merging events with lower Euclidean distance. Numerical results are obtained for rate-1/2 and rate-2/3 nonlinear block encoding binary CPFSK modulation. We show that, for rate-1/2, both newly proposed hybrid approaches outperform conventional ones for the modulation indices of interest, that is, 0\n\n\t\t